I have been buying bitcoin when the price was around 400$-450$.Most of my bitcoins are bought at that price around 40 BTC and remaining at less then 600$ price.i have been holding btc in paper wallet since then and already my stash in usd is 6 times.
here is one of my tx

what i want to know is please suggest some ways to invest my bitcoin at zero risk to earn some profit.Even 0.8% to 1% profit per month is good for me but it should be risk free.i don't mind the profit percentage but risk should not be there.if you have some suggestions please post that too,if i should keep holding for more years and if yes how long should i hold?
is good you sell youre bitcoin
you can get much profit, if you sell last month, with bitcoin price 3000 dollar, i think you can profit receive money 7x this mean equal 120k dollar
and you buy bitcoin only use 400 x 40 16k dollar, fantastic profit